[The definition of "Hu-Chang" in Chinese external medicine].

The Hu-Chang theory is widely used in Chinese external medicine diagnosis and treatment, and it has been documented in many archives and recordings. However, its provenance and connotation were still confusing and unclear. It was believed that The Covert Prescription for External Medicine (Mi Chuan Wai Ke Fang) by Zhao Yizhen in the late Yuan and early Ming Dynasty was the earliest work with the use of provenance from the existing records of Hu-Chang. In terms of its connotation, it was believed by many scholars that the part of speech of Hu-Chang was an adjective-noun phrase, which means "defensive barrier", ie, "local swelling area in surgical disease". However, based on the textual research and analysis of relevant ancient documents, Hu-Chang should be a verb-object phrase, which means "the vital Qi prevents the diseased area from being infected or deteriorated". In this sense, the characteristic of Hu-Chang, the local swelling range of surgical diseases, can be named as "supervising and monitoring the field barrier".